Lighting device

ABSTRACT

The purpose of the present invention is to realize a lighting device of thin, low power consumption and small light distribution angle. The present invention takes the following structure to realize the above task:
         A lighting device having an emitting surface and a bottom opposing to the emitting surface including:   a resin, set between the emitting surface and the bottom, having a hole at a center,   a reflection block set in the hole at a side of the emitting surface,   an LED, which is a light source, set in the hole at a side of the bottom,   a space between the LED and the reflection block,   in which the resin is contained in a container whose inner surface is a reflecting surface.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent ApplicationJP 2020-072759 filed on Apr. 15, 2020, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION (1) Field of the Invention

The present invention relates to the lighting device of thin, smalllight distribution angle, and less power consumption.

(2) Description of the Related Art

Light emitting diodes (LEDs) are being used for the lighting device.Light emitting diodes have high luminous efficiency, and thus profitablefor low power consumption. However, since the light emitting diode is apoint light source, it must be transformed to the surface light sourceif it is used as a lighting device. Besides, if it is used as a spotlight, a light distribution angle characteristics must be considered.

Patent document 1 discloses a lighting device, which uses a lightemitting diode as the light source and to put a collimator lenssurrounding the light emitting diode to collimate the emitting light.Patent document 1 further discloses to dispose a liquid crystal lens atthe light emitting side of the lighting device to control atransmittance, a diffusion, and a deflection of the emitting light.

Patent document 2 discloses a lighting device, which uses a lightemitting diode as the light source and to put a condenser lenssurrounding the light emitting diode; and further to put an opticaldevice at the emitting side of the lighting device to change thedirection of the emitting light. Patent document 2 further discloses touse a liquid crystal lens as an optical device to change the directionof the emitting light.

Patent document 3 discloses to use a liquid crystal lens to control theshape of the light beam.

PRIOR TECHNICAL DOCUMENT Patent Document

Patent document 1: Japanese patent application laid open No. 2019-169435

Patent document 2: Japanese patent application laid open No. 2012-69409

Patent document 3: US 2019/0025657 A1

SUMMARY OF THE INVENTION

The lighting device needs to have a small light distribution angle whenit is used as e.g. a spot light. Conventionally, for such a lightingdevice, a parabolic mirror has been used to form a parallel light.However, a certain depth is necessary in such a lighting device;therefore, it is difficult to attain a small lighting device or thinlighting device. In the meantime, the lighting devices, disclosed inPatent document 1 and patent document 2, need a lens to collimate thelight from the light source; therefore, they need a certain length ofoptical path, consequently, it is difficult to realize a lighting deviceof small depth.

In addition, since a light emitting efficiency of the LED decreases whenthe LED becomes high temperature, it is preferable to be a low heatgenerating light source, namely, low power consuming light source as awhole. Besides, if heat generation from the light source is less, itbecomes not necessary to provide a heat sink and so forth.

The purpose of the present invention is to realize a lighting device ofthin, comparatively less power consumption, and small light distributionangle.

The present invention solves the above explained problems; concretestructures are as follows.

(1) A lighting device having an emitting surface and a bottom opposingto the emitting surface including:

a resin, set between the emitting surface and the bottom, having a holeat a center,

a reflection block set in the hole at a side of the emitting surface,

an LED, which is a light source, set in the hole at a side of thebottom,

a space between the LED and the reflection block,

in which the resin is contained in a container whose inner surface is areflecting surface.

(2) The lighting device according to (1)

in which a plan view of an outer surface of the resin is circular, and across sectional view of an outer surface of the resin is a curved line.

(3) The lighting device according to (1),

in which a plan view of an outer surface of the resin is circular, and across sectional view of an outer surface of the resin is a curved line.

(4) The lighting device according to (1),

in which a plan view of an inner surface of the container, whichcontains the resin, is circular, and a cross sectional view of an outersurface of the container, which contains the resin, is a curved line.

(5) The lighting device according to (1),

in which a thickness of the container, which contains the resin, isthicker at the bottom side than at the emitting surface side in a crosssectional view.

(6) The lighting device according to (1),

in which a surface of the reflection block opposing to the LED is acurved surface.

(7) The lighting device according to (1),

in which a first liquid crystal lens having a circular outer shape isdisposed on the emitting surface,

the first liquid crystal lens has plural lenses extending in a firstdirection and arranged in a second direction.

(8) The lighting device according to (7),

in which a second liquid crystal lens having a circular outer shape isdisposed on the first liquid crystal lens,

the second liquid crystal lens has plural lenses extending in a seconddirection and arranged in a first direction.

(9) The lighting device according to (8),

in which an initial alignment of the liquid crystal molecules in thefirst liquid crystal lens and the second liquid crystal lens ishomogeneous.

(10) The lighting device according to (1),

in which a liquid crystal lens having a circular outer shape is disposedon the emitting surface,

the liquid crystal lens has concentric plural lenses,

the initial alignment of the liquid crystal molecules is homeotropic.

(11) The lighting device according to (1),

in which a liquid crystal lens having a circular outer shape is disposedon the emitting surface,

the liquid crystal lens has a liquid crystal layer between a firstsubstrate and a second substrate,

plural first electrodes formed in concentric are formed on the firstsubstrate,

a disc shaped second electrode is formed in plane on the secondsubstrate,

lens action of the liquid crystal lens is formed by applying differentvoltages to each of the plural first electrodes,

an intimal alignment of liquid crystal molecules in the liquid crystallayer is homeotropic.

(12) The lighting device according to (11),

in which, a refractive index in the liquid crystal lens in the liquidcrystal layer is minimum at a periphery of the liquid crystal lens,

a refractive index in the liquid crystal lens in the liquid crystallayer is maximum at a center of the liquid crystal lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the lighting device;

FIG. 2 is a definition of the light distribution angle;

FIG. 3 is a plan view of the lighting device, which collimates lightwith parabolic mirror;

FIG. 4 is a cross sectional view of FIG. 3 along the line A-A;

FIG. 5 is a plan view of considered first structure;

FIG. 6 is a cross sectional view of FIG. 5 along the line B-B;

FIG. 7 is a plan view of considered second structure;

FIG. 8 is a cross sectional view of FIG. 7 along the line C-C;

FIG. 9 is a plan view of considered third structure;

FIG. 10 is a cross sectional view of FIG. 9 along the line D-D;

FIG. 11 is a perspective view of the lighting device according toembodiment 1;

FIG. 12 is a cross sectional view of FIG. 11 along the line E-E;

FIG. 13 is a plan view of the lighting device according to embodiment 1;

FIG. 14 is a measuring system of illuminance distribution;

FIG. 15 is graphs of a result of illuminance distribution;

FIG. 16A is an example of illuminance distribution when the liquidcrystal lens according to embodiments 2 and 3 are used;

FIG. 16B is an example of illuminance distribution at the irradiatedsurface corresponding to each of the emitting region when a liquidcrystal lens is set on each of the divided emitting region;

FIG. 16C is a cross sectional view in which the emitting surface isdivided into regions to explain the lens action of the liquid crystallens according to embodiments 2 and 3;

FIG. 17 is a cross sectional view of the lighting device according toembodiment 2;

FIG. 18 is a cross sectional view of the first liquid crystal lens andthe second liquid crystal lens;

FIG. 19 is a plan view of the second substrate of the first liquidcrystal lens;

FIG. 20 is a plan view of the first substrate of the first liquidcrystal lens;

FIG. 21 is a plan view of the third substrate of the second liquidcrystal lens;

FIG. 22A is a cross sectional view in which lens action of the liquidcrystal lens is shown;

FIG. 22B is another cross sectional view in which lens action of theliquid crystal lens is shown;

FIG. 22C is yet another cross sectional view in which lens action of theliquid crystal lens is shown;

FIG. 23 is a graph that shows a lens action of the liquid crystal lens;

FIG. 24 is a cross sectional view of another shape of the liquid crystallens;

FIG. 25 is a cross sectional view of another structure of the liquidcrystal lens;

FIG. 26 is a plan view which shows voltages applied to the firstelectrodes of FIG. 25;

FIG. 27 is a cross sectional view that shows a function of the liquidcrystal lens;

FIG. 28 is a plan view which shows an example of voltages applied to thefirst electrodes for lens action of FIG. 27;

FIG. 29A is a cross sectional view of the lens action of the liquidcrystal lens constituted by TN type liquid crystal;

FIG. 29B is another cross sectional view of the lens action of theliquid crystal lens constituted by TN type liquid crystal;

FIG. 30A is a cross sectional view in which a lens action is revealed byapplying a voltage between the comb electrodes;

FIG. 30B is another cross sectional view in which a lens action isrevealed by applying a voltage between the comb electrodes;

FIG. 30C is yet another cross sectional view in which a lens action isrevealed by applying a voltage between the comb electrodes;

FIG. 31 is a plan view of the first electrode of the liquid crystal lensin which lens action is revealed by applying a voltage between the combelectrodes;

FIG. 32 is a cross sectional view of the illuminance distributionaccording to the liquid crystal lenses of embodiments 2and 3;

FIG. 33 is a cross sectional view of the lighting device of embodiment3;

FIG. 34 is a cross sectional view of the liquid crystal lens of FIG. 33;

FIG. 35 is a plan view of the first substrate of the liquid crystal lensof FIG. 34;

FIG. 36A is a cross sectional view of a lens action of the liquidcrystal lens according to FIG. 35 along the line J-J;

FIG. 36B is another cross sectional view of a lens action of the liquidcrystal lens according to FIG. 35 along the line J-J;

FIG. 36C is yet another cross sectional view of a lens action of theliquid crystal lens according to FIG. 35 along the line J-J;

FIG. 37 is a plan view of the first substrate of the liquid crystal lensaccording to embodiment 4;

FIG. 38 is a plan view of the second substrate of the liquid crystallens according to embodiment 4;

FIG. 39 is a cross sectional view which shows lens action of the liquidcrystal lens of embodiment 4; and

FIG. 40 is another cross sectional view which shows lens action of theliquid crystal lens of embodiment 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an example of the lighting device 10, which is used for a spotlight. The light from the lighting device 10 is collimated; a spot light130 is emitted from the emitting surface 110, and irradiates theincident surface 120. The light distribution angle is controlled as e.g.12 degrees to acquire a spot light 130.

FIG. 2 defines the light distribution angle. FIG. 2 shows e.g. that thefloor is irradiated with a spot light emitted from a light emittingsurface 110 disposed on the ceiling. The light intensity is largest atthe normal direction to the light emitting surface 110; the lightintensity decreases according to the polar angle becomes larger. Thelight distribution angle is defined as 2θ provided the intensity alongthe normal direction is 100%, and the intensity along the polar angle θis 50%. In general collimated light, the light distribution angle isrequired as 12 degrees or less.

Conventionally, a parabolic mirror 200 has been used to acquire such acollimated light. FIG. 3 is a plan view of the lighting device 10 usingthe parabolic mirror 200; FIG. 4 is a cross sectional view of thelighting device 10 of FIG. 3. In FIG. 3, the LED 20 is set at the centerof the parabolic mirror 200. The LED 20 is set e.g. on the LED circuitsubstrate 30. The LED 20 is a high brightness LED, which becomes hightemperature; thus, the LED 20 is set on the heat sink 300. A part of theheat sink 300, which is set at the rear of the parabolic mirror 200, isvisible in FIG. 3.

FIG. 4 is a cross sectional view of FIG. 3 along the line A-A. In FIG.4, the LED 20 is disposed at the bottom surface of the parabolic mirror200. The lights emitted from the LED 20, except the light emitted in theoptical axis direction, reflect at the parabolic mirror 200 and becomeparallel to the optical axis. The parabolic mirror 200, however, needsto be as high as h1 for enough collimating function. The height h1 ofthe parabolic mirror 220 needs to be approximately 60 mm to acquire thelight distribution angle of approximately 12 degrees. Actually, sincethe height h2, e.g. approximately 20 mm, of the heat sink 300 is added,the total height of the lighting device becomes 80 mm or more. In themeantime, in the lighting device of FIGS. 3 and 4, one LED, whichconstitutes the light source, needs to be supplied with a large power;consequently, the heat generation in the LED becomes large, thus, theheat sink is indispensable.

The inventors considered the structures of FIGS. 5 through 10 tocountermeasure the problem explained above in relating to FIGS. 3 and 4.FIGS. 5 and 6 are the structures to acquire a collimated light byforming a lens structure between the LED light source and the emittingsurface of the lighting device. FIG. 5 is a plan view; FIG. 6 is a crosssectional view of FIG. 5 along the line B-B. In FIG. 5, the resin 11,which reveals lens effect, is filled in the container 15 whose innerside is mirror. As shown in FIG. 6, a space 12 is formed in the resin11; the LED 20, which is light source, is set at the bottom of the space12. The light from the LED 20 refracts between the space 12 and theresin 11; reflects at the inner wall of the container 15, and eventuallygoes out from the emitting surface 110 of the lighting device.

The light distribution angle can be made as small as e.g. 5 degrees insuch a structure, however, since that structure utilizes refractioneffect of the lens, a certain length of light path is necessary;therefore, a height h1 of the lighting device 10 becomes as high asapproximately 60 mm. Therefore, from the view point of a height h1 ofthe lighting device 10, the structure of FIG. 6 does not give enoughimprovement. In the meantime, a diameter dd of the emitting surface 110of the light emitting device 10 is e.g. 89 mm.

FIG. 7 is a plan view of the lighting device 10 which a height h1 can below. FIG. 8 is a cross sectional view of FIG. 7 along the line C-C. Asshown in FIGS. 7 and 8, the LED 20 as a light source and the LED circuitsubstrate 30 are set at the side of the light emitting surface 110 inthe light emitting device 10, and the lights are reflected at the innerwall, which is constituted as a mirror, of the container 15, thus,collimated lights are emitted.

The structure shown in FIGS. 7 and 8 can make the height h1 of thelighting device 10 low; however, the diameter dd of at the lightemitting surface 110 of the lighting device 10 tends to be bigger ase.g. 110 mm. Further, this structure has difficulty in forming enoughcollimated light, thus, the light distribution angle becomes asapproximately 13 degrees.

The structure of FIGS. 9 and 10 is a third structure of the lightingdevice 10 considered by the inventors; FIG. 9 is a plan view and FIG. 10is a cross sectional view of FIG. 9 along the line D-D. As shown inFIGS. 9 and 10, the resin 11 is filled in the container 15; the LED 20as the light source is set at the bottom of the container 15. As shownin FIG. 10, the curved surface reflector 16 made of metal is setopposing to the LED 20, and is embedded in the resin 11.

As shown by arrows, the lights emitted from the LED 20 reflect at thecurved surface reflector 16 and go to the inner wall, which is made asreflecting surface, of the container 15; then, the lights are reflectedat the inner wall of the container 15 and go out from the emittingsurface 110. In this structure, it is rather easy to acquire a necessarylight path because lights are returned to the direction of the lightsource 20 by the curved surface mirror 16. Therefore, a collimated lightcan be acquired without making a height of the lighting device 10 toohigh; in this case, a height h1 of the lighting device 10 can be as lowas 35 mm. In addition, a diameter dd of the lighting device 10 can bemade small as 75 mm. The light distribution angle of this structure canbe made as approximately 10 degrees.

Embodiment 1

FIGS. 11 through 13 are the lighting device 10 according to embodiment1, which is based on the above structures explained with FIGS. 5 through10 considered by the inventors. FIG. 11 is a perspective view of thestructure of embodiment 1. In FIG. 11, the emitting surface is flat andis formed by resin 11, which has a lens effect. The emitting surface iscircular in a plan view. The upper most portion of the container 15 isvisible at the periphery of the emitting surface. The resin 11 forms twosurfaces at the emitting surface area, namely, a first surface, whichconstitutes the periphery of the emitting surface and a second surfacewhich constitutes recessed central area. The first surface and thesecond surface are connected to each other by inclined third surface.The purpose of forming the recessed region is to control the lightdistribution angle of the emitting light. The reflection block 13 madeof metal is locked in the central area of the recessed portion of theresin 11. The reflection block 13 is circular in a plan view.

FIG. 12 is a cross sectional view of FIG. 11 along the line E-E. In FIG.12, the LED 20 is disposed at the bottom of the lighting device 10; thereflection block 13 is disposed opposing to the LED 20. The reflectionblock 13 is made of high reflection metal as e.g. aluminum. Thereflection block 13 can be formed by resin whose surface, opposing tothe LED 20, is coated by metal film having high reflectance.

The surface, opposing to the light source 20, of the reflection block 13is a curved surface; the opposite surface, namely emitting surface side,of the reflection block is flat. Forming the curved surface is easy ifit is a spherical surface. However, theoretically, the curved surface ofthe reflection block 13 is determined in relation with the inner curvedsurface of the hole formed in the resin 11 and the curved reflectionsurface that corresponds to the outer surface of the resin 11.

Unlike the container of FIGS. 6, 8 and 10, the bottom portion of thecontainer 15 of FIG. 12 is made thick so that the curved surface can bedesigned and manufactured with flexibility, thus, to make the efficiencyof the reflection surface maximum, or to make minimize the lightdistribution angle. A hole is formed at the bottom of the container 15;the hole is filled with the LED 20 and the LED circuit substrate 30.

There is a space 12, where the resin 11 does not exist, between the LED20 and the refection block 13. In the meantime, the space 12 is a holeformed in the resin 11. The hole is circular in a plan view. This space12 is surrounded by lower curved surface of the reflection block 13 andthe inner wall of the resin 11. The inner wall of the resin 11 iscircular in a plan view and is curved line in a cross sectional view.The light emitted from the LED 20 reflects at the lower curved surface(herein after, simply, curved surface) of the reflection block 13, andimpinges in the inner wall of the hole of the resin 11. The light,impinged in the inner wall, refracts in the direction determined bycurved surface of the inner wall, impinging angle to the inner wall, andrefraction index of the resin 11.

The outer surface of the resin 11 is circular in a plan view and is acurved line in a cross sectional view. The inner surface of thecontainer 15 is formed along the outer surface of the resin 11. Thelight entered the resin 11 is reflected at the inner surface of thecontainer 15 and goes to the upper surface of the resin 11, which is anemitting surface. The inner surface of the container 15 is a reflectingsurface to collimate the impinged light. Namely, the reflection surfaceof the container 15 is designed most suitably in relation with thecurved surface of the reflection block 13 and the curved surface of thehole of the resin 11. The thickness of the container 15 is thicker atthe bottom than at the emitting surface in a cross sectional view tofacilitate for designing a suitable curved inner surface. Such acontainer, can be made of metal as e.g. aluminum, can be formed bydie-cast.

The light reflected at the inner surface of the container 15 is furtherrefracted at the emitting surface and goes to outside. The lightingdevice is designed so that the exiting light has a certain lightdistribution angle. In embodiment 1, the recessed portion and theinclined portion are formed at the emitting surface to control the lightdistribution angle finally. A diameter, a depth of the recess and anangle of the inclined portion to form the recess can be determinedfreely. The reflection block 13 is locked at the center of the recess.

In the meantime, the LED 20 becomes high temperature, thus, a heat fromthe LED 20 must be dissipated. In FIGS. 3 and 4, the heat sink 300having fins is disposed to dissipate the heat. In embodiment 1, there isa relatively thick metal container 15 near the LED 20, thus, thecontainer 15 can be used as a heat sink.

Such a lighting device can be formed as following order. At the outset,the container 15 is made of aluminum and is formed with die-cast; theresin 11 is formed in the container 15 with injection molding. A hole,which is circular in a plan view and is curved line in a cross sectionalview, is formed at the center of the resin 11. Then, the reflectionblock 13, which is made of aluminum block, is locked in the hole formedat the center of the resin 11. On the other hand, a hole is formed atthe bottom of the container 15, which is filled by the LED 20 and LEDcircuit substrate 30. As a result, certain distance is made between thelight source of the LED 20 and the reflection block 13.

The lighting device of e.g. a thickness h1 is 30 mm, a diameter dd ofthe emitting surface is 90 mm and the light distribution angle ofapproximately 10 degrees can be realized according to the structureexplained by FIGS. 11 and 12.

FIG. 13 is a plan view of embodiment 1. Most of the area of the emittingsurface 110 is occupied with the resin 11; however, the reflection block13 is locked in the recess of the emitting surface 110. Namely, a lightis not emitted from the center of the emitting surface 110, therefore,non-uniformity in illuminance distribution occurs at the emittingsurface 110.

However, the influence of the reflection block to the non-uniformity inilluminant distribution actually does not occur at the irradiatedsurface. For example, the illuminance distribution at the irradiatedsurface 120, which is 2000 mm distant from emitting surface 110 of thelighting device 10 as depicted in FIG. 14, is shown FIG. 15. The centralgraph of FIG. 15, which has contours, shows contours of illuminationintensities; the unit is W (Watt)/Steradian. In this graph, thehorizontal axis is a polar angle (degree) in the horizontal directionand the vertical axis is a polar angle (degree) in the verticaldirection. The graph in the bottom of FIG. 15 is a graph which shows anillumination distribution in the horizontal direction, in which thehorizontal axis is polar angle (degree) and the vertical axis isintensity of illuminance (W (Watt)/Steradian). The graph in the righthand side of FIG. 15 is a graph which shows a illuminance distributionin the vertical direction, in which the vertical axis is polar angle(degree) and the horizontal axis is intensity of illuminance (W(Watt)/Steradian). As shown in FIG. 15, the reflection block 13 disposedat the center of the emitting surface 110 actually does not haveinfluence to the illuminance distribution at the irradiation surface120.

In the structure of embodiment 1, light loss can be made low if e.g. theresin 11 of high light transmittance like acrylic resin is used, and thereflection block 13 and reflection container 15 of high reflectivity areused. Therefore, the lighting device having a compact outer dimension,high light utilization efficiency and low light distribution angle canbe realized.

In the above specification, it is explained that the plan views of theemitting surface of resin 11, the hole at the center of the resin 11 andthe reflection block 13 are circular; however, this circular shape isnot necessarily be a precise circle, but, e.g. the circular shape can besubstituted by an ellipsis. In the case of the ellipsis, however, if adifference in the diameter of the major axis and the diameter of theminor axis is large, the light distribution angle in the major axis andthe light distribution angle in the minor axis become different.

As described above, according to embodiment 1, a lighting device ofshort depth, small light distribution angle, and high light utilizationefficiency can be realized.

Embodiment 2

Embodiment 2 relates to the structure to control the outgoing light bysetting liquid crystal lens at the emitting surface of the lightingdevice. FIGS. 16A through 16C are conceptual view relating to a functionof the liquid crystal lens. FIG. 16C is a cross sectional view of thelighting device 10. In FIG. 16C, the emitting surface is divided intothe regions of A, B, C and so forth. The light having a predeterminedlight distribution angle is emitted from each of the regions.

FIG. 16B shows an example of illuminance at a distance dz from theemitting surface 110 in FIG. 16C. The vertical axis in FIG. 16B is anilluminance from each of areas A, B, C, and the like; Ad, Bd, Cd, and soforth are distribution of illuminance, which resembles to a normaldistribution. FIG. 16A is a summation of illuminance from each of theareas depicted in FIG. 16B. The vertical axis in FIG. 16A is a summationof illuminance at the irradiation surface 12 from each of the areas atthe emitting surface area 110. FIG. 16A shows the total illuminancedistribution at the irradiated surface 120, a distance dz away from theemitting surface 110, is trapezoidal.

Embodiment 2 is a structure to set a liquid crystal lens at the emittingsurface 110 to control the illuminance distribution at the irradiatedsurface 120, namely, to change the illuminance distribution Ad, Bd, Cd,and so forth at the irradiated plane 120, a distance dz away from theemitting surface 110, by changing emitting light distribution at theregions A, B, C and so forth at the emitting surface 110.

FIG. 17, is a cross sectional view of lighting device 10 of embodiment2. The plan view of FIG. 17 is omitted because it is the same as FIG. 13except that the upper most component of the lighting device 10 is theupper polarizing plate 70 in embodiment 2. In FIG. 17, the structuresfrom the LED 20 through upper surface of the resin are the same as FIG.12, therefore, explanation of those portions are omitted. In FIG. 17,the lower polarizing plate 60 for the liquid crystal lens is set on theresin 11, the lower liquid crystal lens 40 is set on the lowerpolarizing plate 60, the upper liquid crystal lens 50 is set on it, andthe upper polarizing plate 70 is set on the upper liquid crystal lens50.

FIG. 18 is a cross sectional view of the lower liquid crystal lens 40and the upper liquid crystal lens 50. In the lower liquid crystal lens40, the first substrate 41 and the second substrate 42 are adhered toeach other at the periphery thereof through the seal material 45; theliquid crystal 43 is sealed thereinside. In the upper liquid crystallens 50, the third substrate 51 and the fourth substrate 52 are adheredto each other at the periphery thereof through the seal material 55; theliquid crystal 53 is sealed thereinside.

FIG. 19 is a plan view of the second electrode 421 formed on the secondsubstrate 42 of the lower liquid crystal lens 40. FIG. 20 is a plan viewof the first electrode 411 formed on the first substrate 41 of the lowerliquid crystal lens 40. In FIG. 20, the first electrodes 411 extend in ydirection and are arranged in x direction.

FIG. 21 is a plan view of the third electrode 511 formed on the thirdsubstrate 51 of the upper liquid crystal lens 50. The third electrodes511 extend in x direction and are arranged in y direction. The fourthelectrode formed on the fourth substrate 52 of the upper liquid crystallens 50 is the same as the second electrode 421 of the lower liquidcrystal lens 40 shown in FIG. 18. All the electrodes from the firstelectrode through the fourth electrode formed on the liquid crystallenses 40 and 50 are made of transparent conductive film as e.g. ITO(Indium Tin Oxide).

FIGS. 22A through 22C are cross sectional views to explain function ofthe liquid crystal lens, which corresponds to e.g. cross sectional viewalong the line H-H of FIG. 20. FIG. 22A through FIG. 22C are explainedfor the lower liquid crystal lens 40; however, the function is the samefor the upper liquid crystal lens 50. In FIG. 22A, the comb shapedelectrode 411 is formed on the first substrate 41 and the planeelectrode 421 is formed on the second substrate 42. The liquid crystalmolecules 431 are arranged parallel to the substrate if field is notapplied between the electrodes.

FIG. 22B is an example of electric lines of forces LF when a voltage isapplied between the comb shaped electrode 411 of the first substrate 41and the plane electrode 421 of the second substrate 42. FIG. 22C is across sectional view which shows alignment of the liquid crystalmolecules 431 when a voltage is applied to the first electrode 411. InFIG. 22C, the liquid crystal molecules 431 align along the lines offorces LF; consequently, the distribution in refraction is generated,thus, liquid crystal lens is formed. Such a lens is called as thedistributed refractive index type lens GRIN (Gradient Index Lens).

FIG. 23 is an example of the distributed refractive index type lens. Thevertical axis of FIG. 23 is refractive index. The refractive index isminimum on the first electrode 411, which is a comb electrode; therefractive index is maximum at the intermediate position between thecomb electrodes 411. FIG. 23 shows a normal quadratic curve; however,the distribution of the refractive index can be drastically changed by avoltage between the first electrode 411 and the second electrode 412, adistance between the comb electrodes of the first electrode 411, athickness of the liquid crystal layer 43, and so forth. Such function isthe same in the upper liquid crystal lens 50. However, the directions ofthe lens action are perpendicular between in the lower liquid crystallens 40 and in the upper liquid crystal lens 50.

A lens pitch of the liquid crystal lens is often determined by divisionnumber in the emitting surface. On the other hand, a range in thicknessg of the liquid crystal layer in the liquid crystal lens is oftenlimited. FIG. 24 is alignments of the liquid crystal molecules 431 and adistribution of the refractive index when the space s between the combelectrodes 411 is substantially larger than a thickness g of the liquidcrustal layer. In FIG. 24, the vertical axis is a mean refractive indexat each of the positions in the liquid crystal lens; Δneff is adifference of the refractive index in the liquid crystal lens. In thelens in FIG. 24, a lens of small radius of curvature is formed near thecomb electrode 411, and a lens of large radius of curvature is formed atthe intermediate position between the comb electrodes 411.

In some cases, a lens having curvature shown FIG. 24 may be used;however, in other cases a lens having curvature of quadratic curve isneeded. FIG. 25 is a cross sectional view of the liquid crystal lens, inwhich the lens shape is made in quadratic curve or in smooth curvewithout changing a pitch of the lens or a thickness of the liquidcrystal layer. In FIG. 25, one lens is formed by seven electrodes 411,and different voltage is applied to each of the electrodes 411 to alignthe liquid crystal molecules 413 so that refractive index curve becomesa quadratic curve in the liquid crystal lens. In FIG. 25, the voltagesare applied as V1>V2>V3>V4. FIG. 26 is a plan view of the combelectrodes 411 corresponding to FIG. 25. The region B in FIG. 26corresponds to the region B in FIG. 16C.

In some cases, the direction of the light is intended in a certaindirection, not normal to the emitting surface 110. FIG. 27 is an examplein which the light from each of the regions A, B, C, and the like isemitted in the direction of ψ to the emitting surface 110, not normal tothe emitting surface 110. Such function can be attained by shaping eachof the liquid crystal lenses asymmetric.

FIG. 28 is a plan view of the comb electrodes 411 in which voltages areapplied asymmetrically to each of the comb electrodes 411 to make theasymmetric lens. As shown in FIG. 28, the voltages are applied asV1>V2>V3>V4, and V1>V5≠V3, and V1>V6≠V2. As a result, the liquid crystalmolecules 431 are aligned to form an asymmetric lens in the crosssectional view of the liquid crystal lens as shown in FIG. 25.

The liquid crystal lens can be realized not only by the homogeneousalignment liquid crystal as shown in FIGS. 22A or 25 but also by variousother types of liquid crystal devices. FIGS. 29A and 29B are examples inwhich the liquid crystal lens is formed by TN (Twisted Nematic) typeliquid crystal. In the TN type, the liquid crystal molecules 431 rotatetheir alignment direction in 90 degrees between the first substrate 41and the second substrate 42.

FIG. 29A is an example in which a voltage is not applied between thefirst electrode 411 and the second electrode 421. In this case, theliquid crystal molecules 431 are aligned parallel to the first substrate41 or the second substrate 42; however, alignment direction of theliquid crystal molecules 431 changes 90 degrees between near the firstsubstrate 41 and near the second substrate 42. FIG. 29B is an example inwhich a voltage is applied between the first electrode 411 and thesecond electrode 421. In this case, the liquid crystal molecules 431align in vertical direction to the first substrate 41 at directly abovethe comb electrode as the first electrode 411, thus, the light is shut.In the intermediate position between the comb electrodes 411, however,the liquid crystal molecules 431 are not influenced by electric fieldand maintain rotation of 90 degrees with respect to the alignmentdirection near the first substrate 41; thus, transmittance is notinfluenced.

When the structure of FIG. 29B is evaluated as a lens, the refractiveindex is minimum directly above the comb electrode 411 and therefractive index is maximum at the intermediate position between thecomb electrodes 411. Therefore, the distributed refractive index typelens GRIN (Gradient Index Lens) is formed. Various shapes of lenses canbe realized by configuring the electrodes as in FIG. 25 or FIG. 28 evenwhen the lens is formed by TN type liquid crystal.

FIGS. 30A to 30C are cross sectional views in which the liquid crystallens is formed by applying a voltage between the first electrodes 411 ofcomb shape. In FIG. 30A, the comb electrode 411 is formed on the firstsubstrate 41. On the other hand, no electrode is formed on the secondsubstrate 42. The liquid crystal lens is constituted by that the liquidcrystal molecules 431 are aligned by applying a voltage between the combelectrodes, thus, the second electrode 421 is not indispensable. Thesecond electrode is formed by a transparent conductive film as ITO(Indium tin Oxide); however, even a transparent conductive film absorbsor reflects light in certain degree, thus, it is profitable from a viewof transmittance of the lens if the second electrode 421 does not exist.The second electrode 421 may be formed on the second substrate 42 e.g.if the shape of the lens is intended to be changed.

FIG. 30B shows lines of forces LF generated by applying a voltagebetween the comb electrodes 411. The lines of forces LF are directedvertically to the substrate 41 at directly above the comb electrode 411;the lines of forces LF are directed in parallel to the substrate 41 atthe intermediate position between the comb electrodes 411. The liquidcrystal molecules 431 align in the lines of forces LF.

FIG. 30C is a cross sectional view in which the liquid crystal molecules431 align in the field that is depicted in FIG. 30B. In FIG. 30C, therefractive index is minimum at directly above the comb electrode 411 andis maximum at the intermediate position between the comb electrodes 411.Therefore, in this case too, the distributed refractive index type lensGRIN (Gradient Index Lens) is formed.

FIG. 31 is a plan view of the first electrode 411 formed on the firstsubstrate 41. In FIG. 31, the first comb electrode 411 and the secondcomb electrode 411 are nested. The lens depicted in FIG. 30C is formedby applying a voltage between the first comb electrode 411 and thesecond comb electrode 411. Various liquid crystal lens can be formed bychanging a thickness g of the liquid crystal layer, changing a distances between the comb electrodes 411, and changing a voltage V appliedbetween the comb electrodes 411.

As described above, lenses of various functions can be formed not onlyby changing a distance between the electrodes, a thickness of the liquidcrystal layer, and an applied voltage between the electrodes, but alsoby the types of liquid crystal lenses. FIG. 32 shows examples to changethe illuminance distribution by the liquid crystal lens. FIG. 32 is thesame structure as FIGS. 16B and FIG. 16C, however, only emitting lightfrom the region A is shown. FIG. 32 shows that the distribution of theemitting light can be changed in various shapes by the liquid crystallens set in the region A.

In FIG. 32, the illuminance distribution Ad1 resembles to the normaldistribution; the illuminance distribution Ad2 also resembles to thenormal distribution, however, the light is more condensed. Theilluminance distribution Ad3 shows the liquid crystal lens is used as adivergence lens to acquire a trapezoidal illuminance distribution. Theilluminance distribution Ad4 shows a direction of the axis of theilluminance distribution is deviated in polar angle by making the liquidcrystal lens asymmetric.

As explained in FIGS. 16A to 16C, the luminance distribution on thescreen is a summation of the light emitted from each of the regions ofthe emitting surface 110. In other words, the illuminance distributionon the irradiating surface 120 can be changed by changing theilluminance distribution from each of the regions, A, B, C, and the likein the emitting surface 110.

Embodiment 3

FIG. 33 is a cross sectional view of the lighting device according toembodiment 3. In embodiment 3, the lens action of the liquid crystallens is in radial direction. In FIG. 33, only one liquid crystal lens 80is used, other structures are the same as FIG. 12 or 17. The VA(Vertical alignment) type liquid crystal, namely, the homeotropicalignment liquid crystal, is used to form the liquid crystal lens 80whose lens action is in radial direction. Rubbing process or photoalignment process to align the liquid crystal molecules 431 in adirection parallel to the alignment film is not necessary in the VA typeliquid crystal.

FIG. 34 is a cross sectional view of the liquid crystal lens 80; FIG. 35is a plan view of the first electrode 811 formed on the first substrate81 of the liquid crystal lens 80. FIG. 34 corresponds to the crosssection of FIG. 35 along the line I-I. In the liquid crystal lens ofFIG. 34, an electrode is not formed on the second substrate 82; theliquid crystal lens is formed by applying voltages between the ringshaped electrodes of the first electrode 811 formed on the firstsubstrate 81.

In FIG. 35, concentrically formed plural ring shaped electrodesconstitute the first electrode 811. Each of the ring shaped electrodes811 can be applied with voltages independently. FIGS. 36A to 36C, whichcorrespond to a cross sectional view of FIG. 35 along the line J-J,explain the lens function of embodiment 3. FIG. 36A is a cross sectionalview in which a voltage is not applied to the first electrode 811. Sincethe liquid crystal is homeotropic in this embodiment, the liquid crystalmolecules 431 align vertically to the main planes of the first substrate81 and the second substrate 82.

FIG. 36B shows lines of forces LF when a voltage is applied between thefirst electrodes 811. The line of force LF is directed vertically to thesubstrate 81 at directly above the comb electrode 811, and is directedparallel to the substrate 81 at the intermediate position between thecomb electrodes 811. The liquid crystal molecules align along with theline of force.

FIG. 36C is a cross sectional view in which the liquid crystal molecules431 align with the field of FIG. 36B. In FIG. 36C, the refractive indexis minimum at directly above the comb electrode 811 and maximum at theintermediate position between the comb electrodes 811. Therefore, inthis case too, the distributed refractive index type lens GRIN (GradientIndex Lens) is formed.

In this case, each of lenses is formed in radial direction of the ringelectrodes 811 or in radial direction of the circular first substrate 81and the circular second substrate 82. However, the function of each ofthe lenses in the lighting device is the same as explained in FIGS. 16Athrough 16C and FIG. 32 and so forth.

Embodiment 4

This embodiment relates to the structure in which one liquid crystallens as a whole is formed in circular liquid crystal lens. FIGS. 37through 40 show an example of this structure. In the meantime, a crosssectional view of the lighting device as a whole of embodiment 4 is thesame as FIG. 33. Further, the lower polarizing plate 60 and upperpolarizing plate 70 of FIG. 33 and so forth also can be used inembodiment 4. FIG. 37 is an example of the first electrode 811 formed onthe circular first electrode 81. Plural ring shaped electrodes formed inconcentric constitute the first electrode 811. The width of the ringelectrode of FIG. 37 is wider than that of FIG. 35. The leader lines areomitted in FIG. 37.

FIG. 38 is an example of the second electrode 821 formed on the circularsecond substrate 82. The second electrode 821 is formed in disc shape.The liquid crystal is inserted between the first substrate 81 and thesecond substrate 82 to constitute the liquid crystal lens. FIGS. 38 and39 are cross sectional views after the first substrate 81 and the secondsubstrate are assembled; FIGS. 39 and 40 correspond to the crosssectional views of FIG. 37 along the line K-K.

FIG. 39 is a cross sectional view of the liquid crystal lens in which avoltage is not applied between the disc shaped second electrode 821 andthe ring shaped first electrodes 811. In FIG. 39, since the liquidcrystal is homeotropic type, the liquid crystal molecules 431 alignvertically to the major surfaces of the first substrate 81 and thesecond substrate 82. In FIG. 39, r direction means a radial direction.

FIG. 40 is a cross sectional view in which different voltages areapplied to the plural ring shaped first electrodes 811. In FIG. 40, thevoltage applied to the second electrode 821 is V1; voltages V1, V2, V3,V4, and V5 are applied to each of the ring shaped first electrodes 821in order from outside, and V1<V2<V3<V4<V5. The tilting of the liquidcrystal molecules 431 becomes larger according to the voltage applied tothe first electrode 811 becomes lager; and the liquid crystal molecules431 align approximately parallel to the first substrate 81 at the centerof the first substrate 81.

When FIG. 40 is viewed as a liquid crystal lens, refractive index at thecenter of the first substrate 81 is maximum where voltage V5 is appliedto the first electrode 811 and the liquid crystal molecules 431 align inparallel to the first substrate 81; refractive index at the periphery isminimum where voltage V1 is applied to the first electrode 811 and theliquid crystal molecules align vertically to the first substrate 81.Therefore, from the peripheral portion to the center of the liquidcrystal lens, the distributed refractive index type lens GRIN (GradientIndex Lens) is formed. In the liquid crystal lens according to thisembodiment, the lens characteristics can be changed according tovoltages applied to the plural first electrodes 811, number of theplural electrodes 811, thickness g of the liquid crystal layer and soforth.

What is claimed is:
 1. A lighting device having an emitting surface and a bottom opposing to the emitting surface comprising: a resin, set between the emitting surface and the bottom, having a hole at a center, a reflection block set in the hole at a side of the emitting surface, an LED, which is a light source, set in the hole at a side of the bottom, a space between the LED and the reflection block, wherein the resin is contained in a container whose inner surface is a reflecting surface.
 2. The lighting device according to claim 1, wherein a cross sectional view of an inner surface of the hole formed in the resin is a curved line.
 3. The lighting device according to claim 1, wherein a plan view of an outer surface of the resin is circular, and a cross sectional view of an outer surface of the resin is a curved line.
 4. The lighting device according to claim 1, wherein a plan view of an inner surface of the container, which contains the resin, is circular, and a cross sectional view of an outer surface of the container, which contains the resin, is a curved line.
 5. The lighting device according to claim 1, wherein a thickness of the container, which contains the resin, is thicker at the bottom side than at the emitting surface side in a cross sectional view.
 6. The lighting device according to claim 1, wherein a surface of the reflection block opposing to the LED is a curved surface.
 7. The lighting device according to claim 1, wherein a surface of the reflection block at the emitting surface side is a flat surface.
 8. The lighting device according to claim 1, wherein a plan view of the reflection block is circular.
 9. The lighting device according to claim 7, wherein the resin, at the emitting surface side, has a first surface of circular in a plan view, and a second surface at an inner side of the first surface in a plan view, the second surface is nearer to the bottom than the first surface, the first surface and the second surface are connected by an inclined third surface.
 10. The lighting device according to claim 9, wherein the reflection block is located in the second surface.
 11. The lighting device according to claim 1, wherein a first liquid crystal lens having a circular outer shape is disposed on the emitting surface, the first liquid crystal lens has plural lenses extending in a first direction and arranged in a second direction.
 12. The lighting device according to claim 11, wherein a second liquid crystal lens having a circular outer shape is disposed on the first liquid crystal lens, the second liquid crystal lens has plural lenses extending in a second direction and arranged in a first direction.
 13. The lighting device according to claim 12, wherein an initial alignment of the liquid crystal molecules in the first liquid crystal lens and the second liquid crystal lens is homogeneous.
 14. The lighting device according to claim 1, wherein a liquid crystal lens having a circular outer shape is disposed on the emitting surface, the liquid crystal lens has concentric plural lenses, the initial alignment of the liquid crystal molecules is homeotropic.
 15. The lighting device according to claim 1, wherein a liquid crystal lens having a circular outer shape is disposed on the emitting surface, the liquid crystal lens has a liquid crystal layer between a first substrate and a second substrate, plural first electrodes formed in concentric are formed on the first substrate, a disc shaped second electrode is formed in plane on the second substrate, lens action of the liquid crystal lens is formed by applying different voltages to each of the plural first electrodes, an intimal alignment of liquid crystal molecules in the liquid crystal layer is homeotropic.
 16. The lighting device according to claim 15, wherein, a refractive index in the liquid crystal lens in the liquid crystal layer is minimum at a periphery of the liquid crystal lens, a refractive index in the liquid crystal lens in the liquid crystal layer is maximum at a center of the liquid crystal lens. 